1. Field of the Invention
The present invention relates to a reflecting plate, and particularly, to a reflecting plate capable of preventing light from leaking to outside, a backlight and a liquid crystal display (LCD) device having the same.
2. Background of the Invention
Recently, with the development of various portable electronic devices, such as mobile phones, PDAs, notebook computers, etc., a light, thin, small flat panel display device has been in great demand. Research and development are actively conducted for the flat panel display devices, such as an LCD, a PDP (Plasma Display Panel), an FED (Field Emission Display), a VFD (Vacuum Fluorescent Display), etc. Among these devices, the LCD attracts much more attention because of its simple mass-production technique, easy driving system, and implementation of a high picture quality.
The LCD device is a transmissive type display device, and displays a desired image on a screen by controlling an amount of light passing through a liquid crystal layer by a refraction anisotropy of a liquid crystal molecule. Accordingly, the LCD device is provided with a backlight, an optical source passing through a liquid crystal layer for an image display. The backlight is generally divided into an edge type backlight that a lamp is installed on a side surface of a liquid crystal panel thus to provide light to a liquid crystal layer, and a direct type backlight that a lamp is installed below a liquid crystal panel thus to directly provide light to a liquid crystal layer.
According to the edge type backlight, a lamp is installed on a side surface of a liquid crystal panel thus to provide light to a liquid crystal layer through a reflecting plate and a light guide panel. Accordingly, the edge type backlight has a thin thickness thereby to be mainly applied to a notebook, etc. However, the edge type backlight has a difficulty in being applied to an LC panel having a large area since a lamp is installed on a side surface of an LC panel. Furthermore, since light is supplied through the light guide panel, it is difficult to obtain high brightness. Accordingly, the edge type backlight is not suitable for an LC panel for an LCD TV having a large area, one of the most spotlighted LC panel.
According to the direct type backlight, light emitted from a lamp is directly supplied to a liquid crystal layer. Accordingly, the direct type backlight can be applied to a liquid crystal panel of a large area, and a high brightness can be implemented. Therefore, the direct type backlight is mainly used to fabricate a liquid crystal panel for an LCD TV.
As an optical source of the backlight, a Light Emitting Device (LED) which spontaneously emits light, rather than fluorescent lamps, is being used. The LED is an optical source which spontaneously emits monochromatic light such as R, G and B. Accordingly, when being applied to the backlight, the LED implements an excellent color reproduction rate, and reduces driving power.
FIG. 1 is a view showing a structure of an LCD device having a backlight provided with an LED in accordance with the related art, and FIG. 2 is a sectional view of an LCD device in which a backlight and an LC panel are assembled to each other.
As shown in FIGS. 1 and 2, the related LCD device comprises an LC panel 10 composed of a first substrate 1, a second substrate 2, and an LC layer (not shown) disposed therebetween, for implementing an image as a signal is applied thereto from outside; a light emitting device (LED) substrate 32 disposed at a lower side surface of the LC panel 10 and having a plurality of LEDs 34 for emitting light; a light guide panel 35 disposed below the LC panel 10, for guiding light emitted from the LEDs 34 to the LC panel 10; an optical sheet 38 disposed between the LC panel 10 and the light guide panel 35, and consisting of a diffusion sheet 38a and prism sheets 38b, 38c for diffusing and collecting light supplied from the light guide panel 35 to the LC panel 10; a reflecting plate 36 disposed below the light guide panel 35, for reflecting incident light to the LC panel 10; a bottom cover 40 for accommodating therein the reflecting plate 36, the light guide panel 35, the optical sheet 38, and the LED substrate 32; a guide panel 42 having the LC panel 10 therein, for assembling the reflecting plate 36, the light guide panel 35, the optical sheet 38, and the LED substrate 32 with one another by being coupled to the bottom cover 40; and an top cover 46 coupled to the guide panel 42, for assembling the LC panel 10.
The bottom cover 40 serves to assemble a backlight consisting of the reflecting plate 36, the light guide panel 35, the optical sheet 38, the LEDs 34, and has a wall surface upwardly extending from a bottom surface. As components of the backlight are disposed inside the wall surface, the backlight is assembled. The top cover 46 is assembled with the guide panel 42 and the bottom cover 40, thereby assembling the LC panel 10 and the backlight with each other.
In case of using a fluorescent lamp as an optical source, light emitted from the fluorescent lamp may leak to other components rather than the light guide panel 35. In order to prevent this, a lamp housing formed of a metallic material was conventionally disposed on a side surface of the light guide panel, and the fluorescent lamp was disposed in the lamp housing. However, in case of using the LEDs 34 as an optical source, the reflecting plate 36 was used instead of the expensive lamp housing.
More concretely, as shown in FIGS. 1 and 2, the reflecting plate 36 is upwardly extending towards a bottom surface and four side surfaces of the light guide panel 35, thereby facing the four side surfaces of the light guide panel 35. Especially, an extension portion 36b is extendingly formed at the end of the reflecting plate 36 where the LED substrate 32 is disposed, thereby partially covering an upper surface of the light guide panel 35.
The LED substrate 32 is disposed on a rear surface of the reflecting plate 36. Accordingly, a front surface of the LED substrate 32, i.e., a surface where the LEDs 34 are mounted is positioned on the rear surface of the reflecting plate 36. Here, a plurality of windows 36a are formed on the reflecting plate 36 facing the light guide panel 35 and having the LED substrate 32 thereon. Since the windows 36a are aligned with the LEDs 34 of the LED substrate 32, the LEDs 34 faces a side surface of the light guide panel 35 through the windows 36a. That is, the reflecting plate 36 is positioned on a front surface of the LED substrate 32, and only the LEDs 34 are protruding to the reflecting plate 36 through the windows 36a thus to face the light guide panel 35. And, the extension portion 36b is disposed to partially cover an upper surface of the light guide panel 35. Since the bottom surface, part of the upper surface and the four side surfaces (except for the part facing the windows) of the light guide panel 35 are encompassed by the reflecting plate 36, the reflecting plate 36 serves as the lamp housing. This may prevent light emitted from the LEDs 34 from leaking to outside.
However, this LCD device has the following problems.
The windows 36a which encompass the LEDs 34 has a gap between the windows 36a and the LEDs 34. Accordingly, light emitted from the LEDs 34 leaks to outside through the windows 36a, and thus inferiority of an image quality occurs on a screen.